sdcc/device/lib/r3ka/memmove.s

   1 ;--------------------------------------------------------------------------
   2 ;  memmove.s
   3 ;
   4 ;  Copyright (C) 2008-2021, Philipp Klaus Krause, Marco Bodrato
   5 ;
   6 ;  This library is free software; you can redistribute it and/or modify it
   7 ;  under the terms of the GNU General Public License as published by the
   8 ;  Free Software Foundation; either version 2, or (at your option) any
   9 ;  later version.
  10 ;
  11 ;  This library is distributed in the hope that it will be useful,
  12 ;  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 ;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 ;  GNU General Public License for more details.
  15 ;
  16 ;  You should have received a copy of the GNU General Public License
  17 ;  along with this library; see the file COPYING. If not, write to the
  18 ;  Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  19 ;   MA 02110-1301, USA.
  20 ;
  21 ;  As a special exception, if you link this library with other files,
  22 ;  some of which are compiled with SDCC, to produce an executable,
  23 ;  this library does not by itself cause the resulting executable to
  24 ;  be covered by the GNU General Public License. This exception does
  25 ;  not however invalidate any other reasons why the executable file
  26 ;   might be covered by the GNU General Public License.
  27 ;--------------------------------------------------------------------------
  28
  29         .area   _CODE
  30
  31         .globl _memmove
  32
  33 ; The Z80 has the ldir and lddr instructions, which are perfect for implementing memmove().
  34
  35 _memmove:
  36         pop     iy
  37         pop     de
  38         pop     bc
  39         ld      a, c
  40         or      a, b
  41         jr      Z, end
  42         push    hl
  43         sbc     hl, de          ; or above cleared carry.
  44         add     hl, de          ; same carry as the line before
  45         jr      C, memmove_up
  46 memmove_down:
  47         dec     bc
  48         add     hl, bc
  49         ex      de, hl
  50         add     hl, bc
  51         inc     bc
  52         lddr
  53         pop     hl
  54 end:
  55         jp      (iy)
  56 memmove_up:
  57         ex      de, hl
  58         ldir
  59         pop     hl
  60         jp      (iy)
  61